1. Field of the Invention
The present invention relates to an apparatus for obtaining visual images of cornea cells, by which images of cornea endothelium cells of an eyeball of a subject person can be observed or photographed under magnification, and also relates to a method for displaying an imaging-position around the cornea for this type of apparatus for obtaining visual images of cornea cells.
For seeing influences of contact lenses or for medical examination and treatment before and after an operation of cataract, it is necessary to observe the state of cornea endothelium cells. Therefore, for observing or photographing under magnification cornea endothelium cells of an eyeball of a subject person, there have conventionally been used apparatus in which with an objective lens of a microscope of non-contact type or contact type with respect to the eyeball surface of the subject person, slit illumination light is applied toward an observation part obliquely of the eye axis, and its reflected light from the cornea is magnified, in which state the cornea endothelium cells can be observed, or in which apparatus an optimum imaging position where a TV camera or the like is focused on cornea endothelium is detected by the principle of the so-called triangulation method by detecting the position of the reflected light of the slit illumination light from the cornea endothelium, in which state the cornea endothelium cells of the subject part can be imaged by the TV camera or the like.
In these conventional apparatus, the focusing on the cornea endothelium has been accomplished in the following way. That is, the eye axis of the subject is aligned with the optical axis of the microscope by manually moving a microscope frame, which is the main body of the apparatus and which has a TV camera mounted thereon, up and down or right and left with the use of an operation member such as a joy stick so that an alignment indicator light is located at the center of the pupil of the eye on a monitor screen. In this state, the frame of the main body is moved back and forth also manually, so that the focusing is accomplished. However, in making observation or photographing with the above apparatus, there have been demands for observing or photographing under magnification not only the center portion but also various sites of the cornea including peripheral sites, depending on what is examined in the medical treatment. This being the case, it has been difficult to obtain successful images of sites other than the cornea center portion. Also, even when various measures are taken for obtaining such visual images, the view axis is led at discretion of the examiner, so that the imaging site would be difficult to standardize for operational reasons. As a result, visual images of important cornea sites could not be obtained easily.
Further, in order to know an imaging site in obtaining visual images of cornea-peripheral sites, an image of eye-front part illuminated with the alignment indicator light applied to the eyeball surface is picked up by the TV camera, and the position where the imaging site is located generally in the cornea could be known by determining the position of the alignment indicator light from the eye-front image on the monitor with the eye directed along the eye axis, for example, with the eye fixedly viewing a peripheral view target. In this process, since the cornea is transparent and therefore could not be seen, the eye-front image would be observed by referencing the pupil or iris of the eye. Since the iris I is deeper than the cornea 2 as shown in FIG. 8, the cornea 2 moves to an extent more than the iris I as viewed in an imaging direction P. As a result, although an image is picked up at a cornea-endothelium imaging position P.sub.c which is away from a cornea-endothelium center E, i.e., an intersecting point E between the fixed-view direction S and a cornea-endothelium surface 2b by a distance d, yet the image looks from the screen as if it were picked up at a point away from the cornea center by a slight distance AP.sub.0 (see FIG. 9 (b)). As a result, the correct position relative to the pupil center P.sub.0 could not be displayed, as a problem. (In the figure, O is the eyeball rotation center, P.sub.0 is the pupil center, and Q.sub.2 is the cornea-endothelium center of curvature.)
The present invention has been developed in view of the above problems. A first object of the present invention is therefore to provide an apparatus for obtaining visual images of cornea cells, which can lead the view axis of a subject person without the need of decision of an operator (examiner), and which can easily obtain visual images of important cornea sites while it allows the imaging site to be moved (switched), and besides to provide an apparatus for obtaining visual images of cornea cells, which can obtain successful visual images of sites other than a center portion of the cornea.
Another object of the present invention is to provide a method for displaying an imaging position around a cornea in an apparatus for obtaining visual images of cornea cells, which method makes it possible to display an imaging-position mark at a correct position of the eyeball surface on an eye-front imaging screen of the TV camera, in obtaining or photographing a magnified image of cornea endothelium cells around the cornea of a subject eye by the apparatus for obtaining visual images of cornea cells, by leading the view axis of the subject by a doctor.
To accomplish the above objects, the present invention provides an apparatus for obtaining visual images of cornea cells, in which slit light from a slit illumination optical system is applied to the eyeball surface of the subject eye so that a magnified image of cornea cells of the subject part is observed or photographed by the cornea reflected light derived from the slit illumination light via a magnification-imaging optical system, characterized in that a plurality of view targets composed of visible-light sources and opposed to the subject eye are arranged to be switchable one by one by a center-position lighting switch and a peripheral-position lighting-change switch.
Desirably, the plurality of view targets of the apparatus are provided integrally with the magnification-imaging optical system.
Advantageously, the plurality of view targets are composed of a center view target to be positioned on the eye axis of the subject eye and peripheral view targets positioned approximately equal in distance to the center view target in directions of 4 o'clock, 6 o'clock, 8 o'clock, and 12 o'clock around the center view target.
Effectively, the apparatus for obtaining visual images of cornea cells comprises: an illumination optical system for illuminating through a slit an eyeball surface of a subject eye; a magnification-imaging optical system for forming a magnified image of the subject part on an image receiving surface of a TV camera, based on slit illumination light with which the eyeball surface has been illuminated; focusing-detection use receiving optics set in such a position as to receive cornea reflected light of the slit light via at least an objective lens; an eye-front imaging optical system for obtaining a visual image of the eye-front based on the eye-front illumination light; a plurality of view targets including a center view target set as opposed to the subject eye and composed of visible-light sources and arranged so as to be switchable for lighting; an alignment indicator light projection means for projecting alignment indicator light toward the subject eye; a cornea-reflected-light receiving means for receiving cornea reflected light of the alignment indicator light; and a means for moving the imaging system relative to the subject eye depending on output from the light receiving means so that the cornea reflected light of the alignment indicator light is brought to a specified position on a photoreceptor of the light receiving means, wherein the specified position on the photoreceptor can be moved in correspondence to lighting shift of the view targets.
Also, the present invention provides a method for displaying an imaging position around a cornea for use in the apparatus for obtaining visual images of cornea cells, in which slit light from the slit illumination optical system is applied to the eyeball surface of a subject eye and a magnified image of cornea cells of the subject part is observed or photographed by a TV camera from the cornea reflected light derived from the slit illumination light via the magnification-imaging optical system, while an eye-front image corresponding to the magnification-imaging position is photographed by the TV camera via the eye-front imaging optical system, characterized in that an imaging-position mark is displayed at a position calculated from both coordinates of the pupil of the eye on the eye-front imaging screen of the TV camera and coordinates of the cornea-cell imaging position on the eye-front imaging screen.
In the present apparatus, view targets composed of a plurality of visible-light sources and opposed to the subject eye are provided by a center-position lighting switch and a peripheral-position lighting changeover switch so as to be switchable for lighting one by one. By virtue of this arrangement, in observing or photographing a magnified image of cornea cells of a subject part via the magnification-imaging optical system based on reflected light from the eyeball surface illuminated through a slit by the illumination system, only selectively operating the switches allows the view axis of the subject to be led to a required position so that a visual image of a required important cornea site can be easily obtained.
In this arrangement, if the plurality of view targets are provided integrally with the magnification-imaging optical system, the subject eye can be led correctly toward a specified direction when the optical system of the imaging system, after starting operation from its standby position, has reached an imaging position.
In observing or photographing a magnified image of cornea cells of a subject part by leading the view axis of the subject person with this apparatus, if the view targets are provided by a center view target located on the eye axis of the subject person and peripheral view targets positioned approximately equal in distance from the center view target in the 4 o'clock, 6 o'clock, 8 o'clock, and 12 o'clock directions around the center view target, then visual images of standardized important sites of the cornea of the subject person can be easily obtained.
Also, in the apparatus for obtaining visual images of cornea cells, which comprises: an illumination optical system; a magnification-imaging optical system; focusing-detection use receiving optics for cornea reflected light of the slit light via at least an objective lens; an eye-front imaging optical system; a plurality of view targets including a center view target; an alignment indicator light projection means; a cornea-reflected-light receiving means for the alignment indicator light; and a means for moving the imaging system relative to the subject eye depending on output from the light receiving means so that the cornea reflected light of the alignment indicator light is brought to a specified position on a photoreceptor of the light receiving means, the specified position on the photoreceptor can be moved in correspondence to changeover of the lighting of the view targets. Accordingly, when the imaging site is switchedly moved, the apparatus can obtain high-accuracy visual images of the eye front at which the intersecting point of the imaging site illuminated with the alignment indicator light as well as of the subject part by making the imaging direction perpendicular to the cornea surface (cornea endothelium surface or cornea epithelium surface) of the imaging site.
In the method for displaying an imaging site around a cornea, in observing or photographing a magnified image of cornea cells of a subject part by a TV camera via the magnification-imaging optical system based on reflected light from the eyeball surface illuminated through a slit by the illumination system and meanwhile obtaining a visual image of the eye front by the TV camera via the eye-front imaging optical system, an imaging-position mark is displayed at a position calculated by an arbitrary means from two pieces of information, i.e., coordinates of the center of the pupil that can be taken out from the eye-front image of the TV camera and coordinates of a cornea-cell imaging position (known to the machine by the setting of the eye-front imaging optical system and the alignment position) that can be obtained by the movement of the imaging apparatus having the illumination system and the imaging system mounted thereon. By this arrangement, the method allows the correct imaging position, or which site of the cornea a visual image has been obtained at, to be displayed.